Table 2 Risk of bias assessment of observational studies according to Newcastle-Ottawa Scale.

From: Effect of perioperative oral care on postoperative pneumonia in thoracic surgery patients: a systematic review and meta-analysis

Study

Section

Comparability

Exposure

Total

Akutsu et al. 2010

3

1

2

6

Sato et al. 2016

1

1

2

4

Soutome et al. 2016

3

1

2

6

Soutome et al. 2017

1

2

2

5

Ishimaru et al. 2018

4

2

3

9

Mizuno et al. 2018

3

1

1

5

Iwata et al. 2019

2

2

1

5

Shin et al. 2019

4

1

2

7

Yamada et al. 2019

3

2

1

6

Jia et al. 2020

4

2

2

8

Soutome et al. 2020

1

1

1

3

Jia et al. 2021

3

2

2

7

Sekiya et al. 2021

2

1

1

4

Motoi et al. 2022

4

1

2

7

Motoi et al. 2023

4

1

1

6

Abbas et al. 2016

3

1

2

6

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